A check valve is generally referred to as a valve that allows fluid (i.e., liquid or gas) to flow through it in only one direction. Common designs for check valves can include a movable portion, such as a disc or a ball, and a stationary portion that is in connection with the flow path. When sufficient pressure is applied to the inlet, the movable portion can be unseated so that fluid can flow past the movable portion and through the valve. If higher pressure develops on the downstream side, or if fluid flow stops, the movable portion is pressed against the inlet by a spring device to prevent reverse fluid flow.
An insert check valve is a type of check valve that is designed to be positioned between two pipe flanges without the use of a valve body. Insert valves typically include a circular body or “seat”, which is held stationary between the pipe flanges, and a smaller, movable disc that is captured by the seat such that it can open and close with fluid flow. Although there are many types of insert check valves available today, their popularity supports an ongoing need for improvements, for example to features such as sealing and flow properties, response time, weight, cost, and ease of assembly.